This invention generally pertains to alignment and assembly methods for fiber optics with supporting substrates, and to fiber optic devices that are implemented with side-polished fiber optics.
There are no prior art methods and devices published, or on the market, for utilizing the precision of crystal structure(s) to achieve ultra-precise alignments of interacting side-polished fiber. What is known in the prior art deals with implementation of single-fibers that are side-polished to implement two-port photonic functions requiring no side-by-side critical alignment to other fibers. This known art is taught in the U.S. Pat. Nos. 5,809,188 xe2x80x9cTunable optical filter or reflectorxe2x80x9d and 5,781,675 xe2x80x9cMethod for preparing fiber-optic polarizerxe2x80x9d, both by Tseng. Tseng""s patents teach the use of a variable-depth V-groove etched in a silicon crystal substrate to achieve both a) precise control of the remaining side-wall thickness left on a side-polished fiber and b) an arcuate path for the fiber which enables the side-polished region to be of a controlled length. Tseng teaches the use of silicon substrates with 100 crystal orientation at the surface to achieve superior precision in the control of remaining sidewall thickness. He does not teach methods or devices for facilitating the placement of a fiber into a groove of width comparable to the diameter of the fiber. He does not teach means by which to align two fibers end-to-end.
Earlier art teaches side-polished fiber optics made by retaining the fiber within a groove cut into the surface of a non-crystalline material such as glass or quartz. This art can be found in such U.S. Pat. Nos. as 4,493,528 xe2x80x9cFiber optic directional couplerxe2x80x9d, 4,536,058 xe2x80x9cMethod of manufacturing a fiber optic directional couplerxe2x80x9d, 4,556,279 xe2x80x9cPassive fiber Optic Multiplexerxe2x80x9d, 4,564,262 xe2x80x9cFiber optic directional couplerxe2x80x9d, 4,601,541 xe2x80x9cFiber optic directional couplerxe2x80x9d, 6,011,881 xe2x80x9cFiber-optic tunable filterxe2x80x9d, all by Shaw. This art also teaches the requirement of one side-polished fiber along side of a second side-polished fiber, but fails to disclose any means of mechanical self-alignment.
Earlier art also includes devices and methods of aligning optical components using constant-depth V-grooves in the surfaces of silicon substrates. Three examples include U.S. Pat. Nos. 5,633,968 xe2x80x9cFace-lock interconnection means for optical fibers and other optical components and manufacturing methods of the samexe2x80x9d by Sheem, 4,475,790 xe2x80x9cFiber optic couplerxe2x80x9d by Little, and 4,802,727 xe2x80x9cPositioning optical components and waveguidesxe2x80x9d by Stanley. Another U.S. Pat. No., 4,688,882 xe2x80x9cOptical contact evanescent wave fiber optic couplerxe2x80x9d by Failes, not only references some of the earliest work of constructing substrate-supported, side-polished, fiber-optic devices, but also describes some of the limitations involved. This patent by Failes teaches a method of achieving a fused coupling between side-coupled fibers that doesnt""t require the index-matching coupling fluid of previous works. Failes did not offer any approaches to precisely and rigidly support the fibers through intimate contact with respective hard substrates.
Another relevant prior art is that of U.S. Pat. No. 5,187,760 xe2x80x9cWavelength selective coupler for high power optical communicationsxe2x80x9d by Huber. This patent references little of the above prior art, and furthermore, to this inventor""s opinion, seems to be what is called a xe2x80x9cnon-enablingxe2x80x9d patent because it does not provide the reader with information on how to practically implement the structures described and claimed. It describes the use of gratings with which to couple light within a wavelength band between a first fiber and a second fiber. In fact it also describes doing this at more than a single location along the length of the second fiber, wherein the multiple first fibers have respective gratings with different wavelength bands. What is needed is a practicable way in which to implement such structures and devices successfully.
Additional prior art on positioning of fiber optics on substrates is found in the technology of Microelectronic Mechanical Systems (MEMS). One reference to such technology is that of xe2x80x9cMEMS Packaging for Micro Mirror Switchesxe2x80x9d, by L. S. Huang, S. S. Lee, E. Motamedi, M. C. Wu, and C. J. Kim, Proc. 48th Electronic Components and Technology Conference, Seattle, Wash., May 1998, pp. 592-597.
None of the above art teaches methods or devices for facilitating the placement of a fiber into a groove of width comparable to the diameter of the fiber. And none of the above prior art teaches methods or devices to facilitate bringing two fibers end-to-end using a common substrate. Straight and constant-width V-grooves are commonly used in prior-art fiber optic devices, assemblies, and products, but none provide devices and methods by which, in the first place, to facilitate bringing the fiber easily into alignment with these grooves. And fiber optic connectors are common in the prior art with which to bring two fibers into end-to-end alignment, but not using a common substrate and always involving numerous interrelating parts. For example, see U.S. Pat. No. 5,659,647 xe2x80x9cFiber alignment apparatus and methodxe2x80x9d by Kravitz, U.S. Pat. No. 4,919,510 xe2x80x9cOptical connector and methodxe2x80x9d by Hoke, and U.S. Pat. No. 4,682,848 xe2x80x9cUnderwater-mateable optical fiber connectorxe2x80x9d by Cairns.
Practicable methods and devices are needed that manifest a) easy assembly of fibers into precision grooves in supporting substrates; b) easy co-alignment of two independent, precision substrates; and c) easy and precise alignment of fibers end-to-end or of a fiber to a planar waveguide.
Practicable methods and devices are needed that easily manifest precision alignment of fibers side-by-side, and with controlled positional tuning as necessary for fiber optic devices with three or more ports (such as fiber-optic couplers, add-drop multiplexers, taps, splitters, joiners, filters, modulators and switches).
What is also needed is a means to reduce the stress experienced by a fiber optic where it enters or leaves a substrate groove.
Certain objects, advantages and novel features of the invention will be set forth in part in the description that follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned with the practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the methods and devices and combinations particularly pointed out in the appended claims.
The object of the invention is to provide new devices and methods by which to align fiber optics to one another, either side-by-side or end-to-end, or to features in supporting substrates (and devices or features on those substrates), and to align substrates to one another. It is also the object of the invention to provide devices that include alignment grooves having particular alignment-facilitating properties that participate in the moving of a fiber into an alignment groove. The object of the invention is also to include properties that may reduce stress to a fiber where it enters or leaves a supporting substrate. And the object of the invention is to provide facilitating means for using an alignment keying fiber to enable accurate tuning of optical coupling ratio and efficiency of 4-port devices (including 3-port devices) such as fiber-optic side-polished couplers, multiplexers, taps, splitters, joiners, filters, modulators and switches.
These and other objects of the invention are provided by a novel use tapered grooves in supporting substrates, and particularly in crystal substrates having variable-width grooves and in some cases also variable-depth grooves-which are fabricated by etching to form guiding and constraining pathways for fiber optics. The reader will readily appreciate the novel methods and structures used to realize manufacturable fiber optic (and planar optic) devices for performing needed all-fiber photonic functions. Some of the achievements of this invention include the following:
1. A uni-directionally or bi-directionally tapered V-groove for enabling easy positioning of fibers into a precision narrow groove.
2. A precise and microscopically small tapered channel for enabling easy insertion and positioning of a fiber into a precision narrow channel.
3. Substrates with tapered grooves leading to more narrow linear grooves for enabling a fiber to be used as a means of co-aligning a pair of these substrates over a common surface.
4. Substrates with tapered grooves on one surface (face) enabling a fiber to be used as a guide to precisely locate the face of one substrate to the face of another.
5. A bi-directionally tapered groove used for easy alignment of two fibers end-to-end.
6. Substrates with tapered grooves enabling a first fiber in a first substrate to be located end-to-end with a second fiber in an overlapping second substrate. This also allows for precise control of the rotation of the fibers relative to one another, such as when connecting polarization-maintaining fibers end-to-end.
7. Substrates as in 6 above but which also provide for the substrates to cover over the end-to-end fiber interconnection.
8. Method of adjusting interaction length and coupling-ratio in a 4-port side-polished fiber optic device (e.g. coupler or add-drop multiplexer) through the use of an easily positioned fiber as a sliding key in a parallel pair of face-to-face, uni-directionally or bi-directionally tapered grooves.
9. Terminations for fiber optic alignment grooves that provide for minimizing stress and strain at the entry and exit edges of the grooves.